1. Field of the Invention
The present invention relates generally to a container formed from a single die cut blank of paperboard and also to the blank from which it is formed. More particularly, the subject invention pertains to a low cost, hermetically sealed container formed from a single die cut blank in a manner which enables the container to be set up at a relatively high production rate compared with prior art cartons, thus resulting in a container which has substantial economic advantages relative to the prior art.
2. Discussion of the Prior Art
The present invention concerns a carton for products which for various reasons must be enclosed within a package having effective gas and moisture barrier properties. For example, certain products must be protected from exposure to water or moisture, or they may lump, cake, decompose, or otherwise become damaged or harmed. Similarly, other products may be deliberately packaged to include ingredients, such as water or moisture, which cannot be permitted to escape from the product without damaging it in some manner. Typical products which can be packaged in the carton of the present invention include a variety of liquids and solids in powdered, granular or crystalline form such as milk, concentrated fruit juices, powdered sugar, gelatin, salt, flour, cereals, dish-washing detergents and snack foods.
Several approaches have heretofore been used to package these troublesome products. In one approach, the product is packaged in a dual container in which the product is separately packaged within the container in a material having good moisture or gas barrier properties. Breakfast cereals and candies are examples of this type of packaging. In another approach, the material is packaged in a container overwrapped with a material such as a metallic foil which has effective moisture and gas barrier properties. These packages are generally undesirable because they are relatively expensive and, in some cases, require extra steps during the packaging operation which further increases the cost of packaging.
Hermetically sealed cartons of the aforementioned type are frequently formed from paperboard which is continuously manufactured on a paper machine and stored in large rolls. Subsequently, the paperboard is unrolled and directed through an extruder wherein polyethylene is extruded onto one or more surfaces of the paperboard to provide a coating. Thereafter, the thermoplastic coated paperboard is generally rerolled. The coated paperboard is fed into a press which cuts the continuous web of paperboard into container blanks of the desired size. Additionally, the same press may be employed to provide appropriate score lines which facilitate the folding and erecting of the container as well as any printing or art work. Thus, the resulting product is a flat, thermoplastic coated paperboard blank which has been appropriately cut and scored. Generally, at this point, the two longitudinal edges of the blank are joined so as to form a square tube. Commonly, the joining of the two longitudinal edges is achieved through a heat seal, i.e., the polyethylene coating adjacent to the two longitudinal edges is heated and the two heated edges are pressed together. Tubes of the type thus formed are generally sold in a flat condition, by the manufacturing company, to a processor.
When received by the processor, the paperboard tubes are usually sequentially fed into a so-called form, fill and seal machine. Typically, in such a machine, the paperboard tube which was shipped in a flat condition is formed into a square tube and deposited upon an upstanding, square mandrel. The tube is placed on the mandrel so that the part of the tube which will form the bottom of the container extends past the exposed end of the mandrel. Thereafter, the machine proceeds to position the carton under a heater which heats the polyethylene coating on the bottom forming flaps to a temperature at which the polyethylene coating will act as a bonding or adhesive agent. The machine then proceeds to manipulate the flaps extending past the end of the mandrel so as to form a bottom closure. When a bottom closure has been approximately formed by juxtaposing the integral flaps on the tube, the mandrel moves such that a series of cooled plates (pressure pads) are pressed against the formed bottom for a time sufficient to effect a heat seal between the bottom forming flaps. Thereafter, the open top container thus formed is stripped off the mandrel, filled with product and the top is appropriately sealed.
Paperboard cartons of the aforementioned type are disclosed by Arslanian U.S. Pat. No. 3,232,516, Braun U.S. Pat. No. 3,498,524 and Lisiecki U.S. Pat. No. 4,211,357, and are in common commercial usage for products such as milk and juices. Unfortunately, cartons of this type have a number of disadvantages including the following. Major portions of the bottoms of these containers are heat sealed together by four layers of paperboard, which frequently results in problems in their hermetic seals. Moreover, the bottoms of these cartons require a fair amount of detailed work to fold together, insert, and finally seal the various components of the container bottom which result in several disadvantages. The detailed assembly work of the bottom limits the production rate of these containers in a form, fill and seal production line to a present rate, depending upon carton size, of approximately fifty to one hundred and thirty units per minute. Moreover, the detailed insertion and folding together of the bottom component sections requires very accurate die cut blanks and finely adjusted packaging machine mechanisms.
These prior art containers have an additional disadvantage in that the partially assembled blanks received by a processor are difficult to aseptically treat with hydrogen peroxide or other aseptic solutions as they are already partially assembled.